In recent years, as the modularization market of computer-related electronic components/devices becomes more mature, it is much easier for users to assemble a customized desktop computer according to their requirements, thereby resulting in more and more diverse assembly of the personal computer.
However, the existing desktop computers still have room for improvement. In the case of a desktop computer casing (also called casing), the casing is usually exclusively for a particular computer specification. If the user attempts to redesign the computer, he/she usually requires additional purchases of components. For example, a conventional desktop computer generally uses a box structure to accommodate and hold an optical disc drive (ODD), but when the optical disc drive and/or the box structure are removed due to some reasons, it will leave a through hole which was originally for holding the optical disc drive. As a result, the user needs to additionally purchase a dust cover to cover the through hole, or dust will enter into the casing via the through hole. But purchasing and mounting the dust cover increase the product and time costs. In addition, when the dust cover is not needed and removed, it is easily got lost due to careless storage.